Coupling arrangements of this type for the removable coupling of a tool with a manoeuvrable arm of a working machine are previously known. One disadvantage with prior art coupling arrangements is that they are complicated and add a great deal to the distance between the end of the manoeuvrable arm end and the tool. Prior art coupling arrangements normally comprise a separate mounting plate or an intermediate piece, at one side of which the manoeuvrable arm of the working machine is jointed attached while the coupling arrangement itself is attached at the other end of the intermediate piece. Due to the presence of the mounting plate, four shafts are required between the manoeuvrable arm of the working machine and the tool, whereby two shafts are arranged at the intermediate piece and two shafts at the coupling arrangement itself. It is desirable to reduce the need for the said double pairs of shafts. The coupling arrangement becomes unnecessarily heavy through its complexity, whereby the centre of gravity of the working machine is displaced in a disadvantageous manner during extension of the arm.
Prior art fixtures do not have the flexibility that is required to be able to be used with a number of different types of tool independently of the manufacturer and independently of the relative distance between the attachment points of the tool, whereby certain tools may be particularly “tight” and it must be possible to reduce the coupling arrangement a great deal to make it possible to fasten between the attachment points, while other tools may be so “broad” between the attachment points that there is a risk that play arises. Prior art fastening arrangements cannot be adjusted such that the gap or the relative distance between the grippers of the coupling arrangement correspond to the attachment points of the existing tool, which is necessary in order to achieve safe and play-free fastening and to maintain a firm grip during work with the tool.